Tiny 'spherules' reveal details about Earth's asteroid impacts

2012-04-05

Writer(s): University News Service

Researchers are learning details about asteroid impacts going back to the Earth's early history by using a new method for extracting precise information from tiny "spherules" embedded in layers of rock.

The spherules were created when asteroids crashed into the Earth, vaporizing rock that expanded into space as a giant vapor plume. Small droplets of molten and vaporized rock in the plume condensed and solidified, falling back to Earth as a thin layer. The round or oblong particles were preserved in layers of rock, and now researchers have analyzed them to record precise information about asteroids impacting Earth from 3.5 billion to 35 million years ago.

"What we have done is provide the foundation for understanding how to interpret the layers in terms of the size and velocity of the asteroid that made them," said Jay Melosh, an expert in impact cratering and a distinguished professor of earth and atmospheric sciences, physics and aerospace engineering at Purdue University.

Findings, which support a theory that the Earth endured an especially heavy period of asteroid bombardment early in its history, are detailed in a research paper appearing online in the journal Nature on Wednesday (April 25). The paper was written by Purdue physics graduate student Brandon Johnson and Melosh. The findings, based on geologic observations, support a theoretical study in a companion paper in Nature by researchers at the Southwest Research Institute in Boulder, Colo.